ISCHEMIA-REPERFUSION INJURY IN THE RAT-KIDNEY - THE EFFECT OF PRECONDITIONING

Objectives To design and establish a model to examine whether brief pe riods of renal artery occlusion (ischaemic preconditioning, IP) confer s protection from the effects of a subsequent period of ischaemia and reperfusion of the rat kidney. Materials and methods Ninety rats were randomized into six groups, i.e. sham-operated controls; IP alone, a 2 0 or 40 min period of left renal ischaemia (RI) alone: and IP followed by a 20 or 40 min period of RI, Preconditioning involved the sequenti al clamping of the left renal artery for 4 min and its release for 11 min, a total of four times, a 'critical interval' of 30 min before the ischaemic insult. Left renal tissue integrity was determined by dimer capto-succinic acid (DMSA) radionuclide imaging on a gamma-camera both immediately (day 0) and 2 and 9 days later. Acute tubular necrosis wa s also assessed histologically. Results RI for 20 min resulted in a si gnificant decrease in left renal tissue integrity on day 2 only (P < 0 .001), whereas RI for 40 min caused significant left renal dysfunction on day 0, day 2 and day 9 (P less than or equal to 0.01). For a given duration of ischaemia, there was no significant difference between re sults from (IP + RI) rats compared with RI-only rats at any of the thr ee times. There was no significant alteration in renal tissue integrit y in the IP-only rats compared with sham-operated controls. Histologic al findings paralleled the data obtained from DMSA uptake. Conclusions The TP regimen and 30 min 'critical interval' confers no protection t o the kidney from a 20 or 40 min ischaemic episode. The TP regimen its elf appears to have no effect, confirming the validity of our experime ntal model.